Numerous devices have been designed to pulverize materials, for example to turn wheat into flour, coal into coal dust, rock into powder and the like. Some of these devices use hammers, for example and others use rotating blades. For example, U.S. Pat. No. 3,028,103 issued Apr. 3, 1962 to Fisher discloses a comminuting apparatus which uses rotating rotor blades to rotate the material at high velocity, 7,000 rpm and above, using a rotor with a radius of about 6 inches, and having vortex-creating members on the inner wall of the casing to generate turbulence. The action of the air vortices on the material apparently results in comminution. U.S. Pat. No. 3,224,85 issued Dec. 21, 1965 to Brack et al. also discloses an apparatus for comminuting materials which uses a rotor having a series of radial impellers rotated at high speeds, on the order of 3,600 rpm. with rotors of 18 inches or 24 inches in diameter. Here pulverization is carried out apparently by eddy currents of air. These prior devices are sufficiently small, and require sufficiently high angular velocities, that a high throughput may not be economic. These prior art devices also require air in order to operate.
The present invention uses a rotating rotor to pulverize materials in a manner which can be operated in a vacuum. It has also been found that a much larger rotor, using a much lower angular velocity, can achieve efficient pulverization with a high throughput.